This invention relates to a new use for the type of polyphosphonate material that is described and claimed in U.S. Pat. Nos. 4,331,614 and 4,719,279, which are each incorporated herein by reference. While U.S. Pat. No. 4,035,442 has described polyester filaments having improved flame retardancy due to use of a poly(m-phenylene cyclohexylphosphonate), the instant invention relates to flame retarded epoxy compositions, as will be described in greater detail below. The term “polyphosphonate” as used herein is to be construed as covering oligomeric phosphonate materials as well as those of higher molecular weight.
Shouji Minegishi describes the reaction of epoxy compounds with phosphonates in Journal of Polymer Science, Part A, Polymer Chemistry, Vol. 37, 959-965:
His goal was to prepare polymeric linear phosphonates with little or no residual epoxy. Such polymers can be used as additive type flame retardants.
The present invention relates to an epoxy resin composition that can be used, for example, in printed wiring boards for electronic applications. It represents a new embodiment, for example, over the type of flame retarded epoxy resin compositions described in PCT Patent Publication No. WO 03/029258 where an epoxy resin, which contained the type of polyphosphonate flame retardant additive that is also used in the epoxy resin compositions of the present invention, was cured in the presence of a methylimidazole curing catalyst.